Photographic light-sensitive materials are generally composed of a base having an electrical insulating property and photographic layers, and electrostatic charges are easily accumulated due to rubbing friction between surfaces of the same kind or different kinds of materials or separation thereof in the steps of producing the photographic light-sensitive materials or during use thereof. These accumulated electrostatic charges cause many problems. The most serious problem is that electrostatic charges accumulated before development processing cause dotted spots or resinous or feathered markings when carrying out development processing of the photographic film, because the light-sensitive emulsion layer is sensitized by discharging. This is the so-called "static mark", by which commercial value of a photographic film is greatly damaged or is sometimes completely lost. For example, it is easily recognized that when such static marks appear on medical or industrial X-ray films, erroneous judgments may be induced. This phenomenon is also very troublesome because it is only confirmed upon development. Further, these accumulated electrostatic charges induce secondary problems, for example, dusts adhere to the surface of films or uniform application can not be carried out.
As noted above, such electrostatic charges are easily accumulated during production of the photographic light-sensitive materials and use thereof. For example, during production steps, they can be generated by rubbing friction between the photographic film and a roll, or by separation of the emulsion face from the base in a step of winding or rewinding the photographic films. Further, they can be generated by contact with or separation from machine parts or fluorescent sensitizing paper in automatic photographing machines for X-ray films. In addition, they can be generated by contact with packing materials.
Such static marks on the photographic light-sensitive materials induced by accumulation of electrostatic charges becomes remarkable with increases in sensitivity and increases in processing rates. Particularly, in recent years, generation of static mark has tended to be easily caused because of increasing use of photographic light-sensitive materials having high sensitivity, and because such materials are frequently subjected to severe handling, such as high speed application of photographic layers to a base, high speed photography, high speed automatic processing, etc.
In order to overcome these problems due to static electricity, it is preferred to add antistatic agents to photographic light-sensitive materials. However, antistatic agents used generally in other fields of technology can not always be used for photographic light-sensitive materials, and they are subjected to various restrictions specific to photographic light-sensitive materials. Namely, antistatic agents capable of utilization for photographic light-sensitive materials require not only excellent antistatic performance, but also other properties, for example, (1) they should not have any adverse influence upon photographic characteristics of the photographic light-sensitive material, such as sensitivity, fog, granularity, sharpness, etc., (2) they should not have an adverse influence upon the physical properties of the photographic light-sensitive material (e.g., the film is not easily damaged by friction or scratching), (3) they should not have an adverse influence upon antiadhesive characteristics (i.e., the surface of a photographic light-sensitive material should not easily adhere to the surface of another photographic light-sensitive material or other surfaces), (4) they should not promote fatigue of processing solutions for photographic light-sensitive materials, and (5) they do not promote deterioration of adhesive strength between layers in the photographic light-sensitive material. Accordingly, application of the antistatic agents to photographic light-sensitive materials is subject to many restrictions.
One method for overcoming problems due to static electricity is to increase electric conductivity of a surface of the light-sensitive material, so that electrostatic charges disappear in a short time, before the electric charge can accumulate and discharge with adverse effects.
Therefore, it has been attempted hitherto to increase electrical conductivity of the base or various surface layers in photographic light-sensitive materials by utilizing various hygroscopic substances or water soluble inorganic salts, certain kinds of surfactants and polymers, etc. For example, it has been known to use polymers as described in U.S. Pat. Nos. 2,882,157, 2,972,535, 3,062,785, 3,262,807, 3,514,291, 3,615,531, 3,753,716 and 3,938,999, etc., surfactants as described in U.S. Pat. Nos. 2,982,651, 3,428,456, 3,457,076, 3,454,625, 3,552,972 and 3,655,387, etc., and metal oxides and colloidal silica as described in U.S. Pat. Nos. 3,062,700, 3,245,833 and 3,525,621, etc.
However, it is very difficult to generalize the use these substances for photographic light-sensitive materials, because (1) these substances show specificity depending upon the kind of film base or photographic composition, and they are not useful for preventing electrification in certain film bases and photographic emulsions or other photographic elements, though they may provide good results in some other film bases and photographic emulsions or photographic elements, or (2) they have an adverse influence upon photographic characteristics of photographic emulsions, such as sensitivity, fog, granularity, sharpness, etc., even though they might have an excellent antistatic characteristics, or (3) the antistatic characteristic deteriorates with the passage of time, even though the photographic light-sensitive material might have an excellent antistatic characteristic just after production.
British Pat. No. 861,134, German Pat. No. 1,422,809, and U.S. Pat. No. 3,850,641 have disclosed that an excellent effect in preventing electrification is obtained by incorporating polyoxyethylene type surfactants in photographic light-sensitive materials.
However, such photographic light-sensitive materials containing polyoxyethylene type surfactants have had a serious fault. Namely, when the photographic light-sensitive materials containing the polyoxyethylene type surfactants are stored prior to use under high temperature conditions (e.g., 40.degree. C. or higher), blackened silver is deposited in nonexposed areas during development as well as in exposed areas; i.e., such surfactants have a tendency to cause fog. This can be a fatal fault in photographic light-sensitive materials, because it can significantly deteriorate the quality of the photographic images.
In order to prevent the occurrence of fog, it has been a general practice in the silver salt photographic field to add organic heterocyclic compounds, as described, e.g., in Stabilization of Photographic Silver Halide Emulsion Dr. E. J. Birr, Focal Press, London-New York, pages 52-99, 1974; Shashinkogaku no Kiso, Chapter entitled Silver salt photography, edited by Nippon Shashin Gakkai, Corona Co., pages 189-204, 1979; and Japanese Patent Application (OPI) No. 164,734/82 (the term "OPI" as used herein refers to a "published unexamined Japanese patent application") to photographic light-sensitive materials. However, if organic heterocyclic compounds are added to photographic light-sensitive materials in which the polyoxyethylene type surfactants are used for the purpose of improving antistatic performance, fog can not be effectively prevented. Particularly, if it is intended to prevent occurrence of fog by increasing the amount of the organic heterocyclic compounds, the effect can be recognized to some extent, but photographic sensitivity, which is the single most important property of the photographic light-sensitive material, deteriorates significantly. Consequently, the amount of the organic heterocyclic compounds that can be used is restricted, and fog can not be substantially prevented.
Thus, as described above, it has been difficult to effectively prevent the occurrence of fog in photographic light-sensitive materials in which the antistatic property is provided by adding polyoxyethylene type surfactants.